Apparatus for imparting stresses to structural members



Sept. T.r R.A CROM APPARATUS FUR -IMPARTTNG sTRRssEs To STRUCTURAL MEMBERS 4Fiecmune 16. 195s s sheets-sheet 1 FIGI. ff@

INVENTOR. THEODORE R. CROM MUST' FIG.

Sept. 23, 1958 T, R, CROM 2,853,250

APPARATUS FOR IMPARTING STRESSES TO STRUCTURAL MEMBERS FlG.6.

INVENToR. V THEODOBE R. CROM T. R. cRoM sept. 23, 195s APPARATUS FOR IMPARTING STRESSES TO STRUCTURAL MEMBERS Filed June 16, 1953 ifa@ cRoM

\ /s Arm/B3. y

INVENTOR. THEODORE R.

United States Patent APPARATUS FOR IMPARTING STRESSES TO STRUCTURAL MEMBERS Theodore R. Crom, Gainesville, Fla., assigner to John Maurice Crom, McAllen, Tex.

Application June 16, 1953, Serial No.` 361,984

9 Claims. (Cl. 242-1) This invention relates to a method and apparatus for imparting a stress to structural members, and more particularly it relates to a method and apparatus for prestressing beams, slabs or the like, by winding wire under tension thereon.

A method of prestressing structural members has been described in my copending application Serial N-o. 335,233, tiled February 5, 1953,-in which a structural member and a tensioned wire are Wound relative to each other, and deflectors are utilized to position the wire in a desired pattern on the member. In the preferred embodiment described in the copending application the structural member is rotated. This method has been found highly practical for many prestressing purposes, particularly for reinforcing slabs and beams. However, its application is limited somewhat by the fact that it is frequently diiicult or even impossible to rotate a relatively large beam or slab, and of course this would be impossible where the member is already set in a fixed position in a building structure.

In accordancewith the method of the present invention, the structural member to be stressed is in a fixed position. It may be held in this position due solely to its weight, or itmay be fastened by bolts or other fastening means. The wire is moved relative to the fixed structural member. More particularly, the wire under tension is wound around the structural member and during the winding the wire is deliected so as to position it at different locations on different parts of the structural member to impart the desired stress pattern.

In accordance with the apparatus of the invention, a traction vehicle is provided which is movable relative to the structural member with means mounted on the velhicle to position the wire in the manner described as the vehicle moves relative to the structural member. The vehicle may have different forms, as described hereinunder, and the means for positioning the Wire relative to the structural member may have different embodiments, as will be described.

For a more complete understanding of the present invention, reference may be had to the accompanying drawings forming a part of the speciiication wherein:

Figure 1 is a side elevation of one form of the invention which is partly broken away to show the inner details thereof; l

Figure 2 is a view in section taken through line 2-2 of Figure l;

Figure 3 is a partial view in section taken along line 3-3 of Figure l showing the wire guide control mechanism;

Figure 4 is a partial view in section taken along line 4-4 of Figure 1 showing the end of a beam and the wire guide mechanism;

Figure 5 is a side elevation partly in section showing another form of this invention;

Figure 6 is a view in section taken along line 6-6 of Figure 5;

Figure 7 is a partial View in section taken along line 7-7 of Figure 5;

Figure 8 is a side elevation of another form of this invention which is partly broken away to show the inner details thereof;

Figure 9 is a partial View in section taken along line 10--10 of Figure 8; and

Figure l0 is a perspective View showing details of the deflectors and post guiding mechanism mounted on and adjacent to a beam. v

Referring first to Figures l and 2, a four wheel vehicle 10 is driven by a motor located within a motor housing 11 positioned on the upper forward portion of a vehicle frame or chassis 12. A seat 14 for the vehicle operator is mounted on vthe upper rearward portion of the chassis 12, adjacent to a control panel 15. A steering wheel 16, a hand brake 17 and a gear shift lever 18 are provided to control the vehicle along with the conventional foot clutch and brake.

The mechanical arrangement for steering and controlling the vehicle as well as the mechanical means for driving it, are of conventional design and do not form a part of this invention. The vehicle maybe driven forward or backward by one or more chains extending to the wheels 9. However, it will be noted that an important feature of this vehicle design is its relatively high clearance between the ground 19 and Ithe underside 26 of the chassis 12, so that the vehicle may be driven over a beam as will be described later.

A hollow wire guide post 25 of hexagonal cross section extends vertically through laterally extending slots 26, 26a and 26h formed near the center in each of three horizontal frame members 27, 27a and 27b of the vehicle frame 12. The upper end 2S of the post 25 is slidably mounted through openings 30 and 31 in both ends 32 and 33 of an hydraulic cylinder 34. A piston or plunger 35 is formed concentrically about the post 25 within the cylinder 34, and is movable in sliding engagement with the inner wall 37 thereof.

An opening 33 extending through the side of the hydraulic cylinder 34 communicates with that portion of its hollow interior disposed between the lower surface 35a of the piston 35 and the adjacent end 33 of the cylinder. The opening 38 is connected with an hydraulic pressure source by a ilexible hydraulic pressure line 40. The hydraulic pressure source may be of any type well known in the art.

The ilow of the hydraulic pressure through line 40 and the venting of the pressure accumulated in the cylinder 34 (also through line 4(3) is controlled by a valve or other suitable means apparent to one familiar vwith the art, which in turn is operated by a valve switch 45 mounted on the instrument panel 15. Thus, when the switch 45 is set in one position, hydraulic liuid is admitted to the hydraulic cylinder 34 and the piston 35 and post 25 are raised. When the switch 45 is set in another position, the pressure accumulated in the cylinder 34 is vented, and by the force of gravity the piston 35 and post 25 are lowered. If desired, hydraulic fluid may be applied to thel top of the piston to lower it.

The hydraulic cylinder 34 is mounted between and secured to a pair of supporting members 48 and 49. Each of the members 48 and 49 has a pair of horizontally disposed, outwardly extending shoulders 53, 54 and 55, 56. Each of these shoulders has an opening which is adapted to slidably receive two pairs of horizontal bars 64, 65 and 66, 67. With particular reference to Figure 2, it will be seen that the bars 64, 65 and 66, 67 are supported at their respective Aopposite ends by brackets 70 and 71 secured to two opposite vertical frame members 72 and 73. lt will therefore be appreciated that the cylinder 34 and post 25 are free to move laterally back and forth on the bars 64, 65 and 66, 67 in respect to the chassis 12. v

The center portion of the post 25, whlch 1s of heXag' onal cross-section, extends through a corresponding?) shaped opening 79 in a rack member 80 whlch has two pairs of horizontal and outwardly extending upper land lower shoulders 84, 85 and S6, 87 which are recelved within corresponding grooves 89 formed in the adjacent sides of horizontally disposed carriage members 94a, 94h and 95. The said carriage members are disposed between the middle and lower horizontal frame members 27a and 27b, and are secured to the frame members 27a and 27b by suitable means Ysuch as bolts and nuts 96. The carriage members 94a and 94b are separated by an opening or gap generally indicated at 98.

The rack member 80 is provided with a row of teeth 99 formed on the outer edge of a horizontally extending shoulder 100 between the adjacent supporting shoulders 84 and 85. The shoulder 100 extends through opening 98 between the carriage members 94a and 941;. A pinion 102 keyed to a vertical shaft 103 meshes with the rack teeth 99. The shaft 103 is journalled at its lower end through an opening 104 in the lower carriage member 94h. The upper portion of the shaft 103 extends through openings 105 and 106 formed in the upper carriage member 94a and the middle horizontal frame member 27a.

The shaft 103 is driven by a set of meshing beveled gears 108, which in turn are connected with suitable reversible clutching means and with the motor of the vehicle 10. The reversible clutching means does not form a part of this invention and any one of many suitable mechanical arrangements apparent to one skilled in the art may be used. In addition, it is to be understood that an independent hydraulic system, similar to that disclosed for raising and lowering the guide post 25, may be used to move the post 25 from side to side.

A suitable control 45a for operating the above-mentioned clutching means and thereby engaging and driving the rack pinion 102 may be mounted on the control panel 15. Thus, when the clutching means is engaged and the rack pinion 102 is driven, the rack member 80 (and post 25) is moved to one side of the chassis 12 or the other, between the carriage members 94a and 94h and 9S. At the same time, the hydraulic chamber 34 is shifted along the bars 64, 65, 66 and 67. Also in this connection, it will be appreciated that the post 25 may be raised or lowered while it is being shifted laterally in respect to the chassis 12.

The lower end 110 of the guide post 25 is received through an opening 111 in a die box 112. Formed integral with the extreme end of the post 25 is a circular shoulder 114. Bearings 115 are disposed between the circumferential side of the shoulder 114 and the inner vertical wall 118 of the die box 112, and thus the latter is free to rotate with respect to the post 25. A wire drawing die 120 is mounted within an opening 121 which extends through the side 122 of the die box 112. A pair of guiding rollers 155 and 156 is mounted within the die box 112 to guide the wire as it leaves the end of the post 25 and passes through the die 120. A predetermined tension is required to draw the wire through the die, and the wire is reduced in diameter depending upon the size of the die opening. It will be understood, of course, that other tensioning devices well known to one skilled in the art may be used in place of the die, as for example, a braking apparatus wherein several turns of wire are wound about a capstan member which is braked to turn only when the wire is subjected to a given tension.

A coil of wire 125 is carried upon the upper side of the vehicle by means of a large wire reel 126. The reel 126 is rotatably supported upon a horizontal shaft 127, the ends of which extend through openings formed by arcuate surfaces 129 in the upper ends of two vertically disposed stanchions 131 and 132and arcuate spilt; bearing members 133. The spllt-bearlng members 13o are secured to the upper ends of the stanchions 131 and 132 by bolts 137. The lower ends of the stanchions 131 and 132 are secured to the upper horizontal frame member 27, adjacent to the motor'housing l11. The w1re (W), as this word is used herein, is carried by the reel 126 and may be formed of iron or steel of any composition, nylon or other plastic or fibrous glass and thellke, the latter materials having been found highly satisfactory for many prestressing purposes because of their relatively low cost and non-corrosive propert1es.

When the apparatus is used for applying wire to a beam, as will be described hereinafter, the wire W 1S removed from the reel 126 and passes through a wire guiding mechanism mounted on top of the control housing 143. The wire guiding mechanism 140 includes two adjacent pairs of vertically and horizontally disposed rollers 146 and 147 which are rotatably supported by a frame member 148 (see Fig. 2). The frame 148 is secured to the housing 143 by bolts 149. It is to be understood, of course, that other wire guiding means may be used.

The wire W extends from the wire guiding mechanism 140 downwardly through a slot 152 in the control housing 143, and then passes through the hollow center portion of the guide post 25, around the rollers and 156 and then through the die 121.

The apparatus may be used for winding wire on structural members of any dimension and shape, such as beams and slabs, which may be of any material, such as iron, wood, concrete, cement blocks or other material. As will be seen in Figures l and 2, a beam is positioned in a xed position upon the ground or other support such as in a building structure. If the beam is large its weight will hold it in fixed position. If it is small it may be secured by any fastening means.

The beam 160, which is shown as illustrative, has a horizontally extending groove 161 formed about its vertically disposed sides 163, 164 and its ends 167, one of which is shown. Near the ends 167 of the beam 160 the width of the groove 161 is gradually increased (as indicated at 161a) so that at the extreme ends 167 of the beam 160 the width of the groove 161 is the greatest. Of course this groove construction may be modified depending upon the prestressing effect desired. This aspect of the invention is described in detail in my copending application 335,233, led February 5, 1953.

The free end of the wire W is first secured to the beam or to the ground, and then the vehicle 10 is driven back and forth along the entire length of the beam, with the wheels of the vehicle straddling the beam. As the vehicle is moved, the Wire W is drawn from the die box 112 and deposited within the groove 161, as the guide post approaches an end 167 of the beam 160 (as shown in Figures 1 and 4) the operator raises the guide post 25 by operating the hydraulic cylinder 34, so that the wire is raised to the desired position Within the groove about the ends of the beam. When the vehicle reaches the end of the beam the operator engages the previously described clutching mechanism and thereby shifts the rack member S0 and the post 25 across the end of the beam and in so doing the tensioned wire W strikes a corner 168 of the beam, causing the die box 112 to rotate counter-clockwise approximately 90 degrees.

When the post 25 is shifted to the opposite side of the beam (as shown in dotted lines at 169 in Figure 4), the operator then drives the vehicle towards the opposite end ofthe beam. When the tensioned wire W strikes the opposite corner 170 of the beam, the die box 112 is again rotated counter-clockwise an additional 90 degrees. At the same time or shortly thereafter the operator lowers the post by means of the piston 134 so that the die box 112 is I,once again placed on the same level as the groove 161.

On succeeding loops of the wire the postV 25 may be raised a progressively lesser distance so that the subsequent loops of wire will be disposed adjacent to and just beneath each preceding loop -of wire.

With reference to Figure 4, it will be seen that as the tensioned wire W is wound about the end 167 of the beam 160, the side 163 and corner 168 thereof are subjected to a considerable force which may tend to tip the beam over on its side. To prevent this from happening, and to hold the beam 160 firmly in position in relation to the wire winding mechanism, the vehicle is equipped with two pairs of hydraulically operated beam supporting members 175 and 17 6 which extend downwardly from the underside of the chassis 12. Each of the beam supporting members 175 and 176 has adjustable, inwardly-extending, horizontal members generally indicated at 177 and 178, which in turn have inverted L-shaped abutment members 179 and'180 (see Fig. 2) formed on the ends thereof.

As can best be seen in Figure 5, the supporting members 175 and 176 are shifted downwardly to the level of the beam by hydraulic mechanisms generally indicated at 181 when the vehicle reaches the end of the beam. When the hydraulic pressure therein is released, the supporting members 175 and 176 are shifted upwardly away from the beam by means of a coil spring 182 disposed within the hydraulic mechanisms 181. The horizontal members 177 and 178 may be moved towards the sides 163 and 164 of the beam 160 by a rack and pinion arrangement diagrammatically illustrated at 184 in Figures 2 and 6. The rack and pinion mechanisms 184 may be hydraulically operated or they can be adjusted lby hand before the winding operation is commenced.

The hydraulic mechanism 181 which raises and lowers the beam supporting members 175 and 176 may be operated by suitable controls mounted on the control panel 15. Also the rack and pinion mechanisms 184 may be pre-adjusted for beams of a given width or may be operated by suitable controls mounted on-the instrument panel 15. Thus, as the vehicle and the wire guiding post approach the end 167 of the beam (before the post is shifted laterally in respect thereto) the operator may conveniently lower the rearward pair of supporting members 175 into engagement with the sides of the beam.

It is to be understood, of course, that other means, apparent to one skilled in the art, may lbe utilized to support the ends `of the beam as the wire is wound thereon.

Figures 5 and 6 illustrate another embodiment of my invention in which a wire conveying vehicle 189 of the same general design -as that disclosed previously. However, it will be noted that the wire guiding mechanism generally indicated at 190 is of modified design.

The wire guiding mechanism 190 is formed by a hollow shaft 191 which has a cantilever extension generally indicated at 192 secure to the lower end thereof. The shaft 191 is vertically disposed and extends downwardly through openings 194 and 195 in the upper and lower horizontal frame members 196 and 197. The center and lower portion 200 o-f the shaft 191, which is of hexagonal cross-section, has collars 201 and 202 slidably mounted thereon. The collars 201 and 202 are rotatably supported by a pair of concentrically mounted bearing assemblies, generally indicated at 204 and 205, which in turn are secured to the upper and lower frame members 196 and 197.

An annular gear 210 having an hexagonal center opening is slidably mounted a out the middle portion 200 of the shaft 191 just above the upper bearing assembly 204. Inasmuch as the shaft is of hexagonal cross-section and fits within the hexagonal opening in the gear 210, rotation of the gear 210 rotates the shaft 191. The gear 210 has a downwardly extending collar or hub 211 which is re- -ceived within a cylindrical member 212 having a base ange 214 formed about the opposite end thereof. The base ange 214 is secured to the upper horizontal frame member 196. Ball bearings 215 are supported between cooperating raceways 216 and 217 formed about the collar or hub 211Vof the gear 210 and the inner surface of the cylindrical member 212, respectively, which permit the gear (and shaft) to rotate.

The gear 210 is driven by a worm gear 218 carried by a shaft 219. With reference to Figure 5, the righthand end of the shaft 219 is rotatably supported by a bushing 220 secured to a vertical frame member 221. The opposite or lefthand end of the shaft 219 may be drivingly engaged with the vehicle engine by any suitable means apparent to one skilled in the art.

The shaft 191 is raised or lowered by an hydraulic cylinder 225 lwhich is connected near the upper end 208 thereof. This hydraulic arrangement may be the same as that shown in Figures 1 and 2. However, it is to be understood that other hydraulic or mechanical means apparent t-o one skilled in the art may be used for this purpose. Also, similar to the previously described modification, the operation of the hydraulic cylinder as well as the rotation of the gears 210 and 218 is controlled by suitable controls mounted on the instrument panel or in a convenient position adjacent the drivers seat.

The cantilever extension 192 mounted on the lower end of the shaft 191, is formed of horizontal and vertical members 227 and 228. The horizontal member 227 includes a pair of symmetrically shaped sections 22711 and 227b (see Figure 7), each of which has two arcuate portions 230 and 231. When the sections 227a and 227 b are drawn together by bolts 233, the adjacent arcuate portions form two openings; one of hexagonal design which receives the lower end of the shaft 191, and the other of circular shape for receiving a portion of smaller diameter of the vertical member 228.

A tensioning mechanism 238 similar to the type described in Figs. 1 to 4 is rotatably mounted on the lower end of the vertical member 228 by means of bearings 240 which are carried by concentric grooves or raceways 241 formed about the inner surface 243 of its housing 244, and corresponding raceways 248 formed about the end of the vertical member. Thus the ten* sioning mechanism 238 is held in a xed longitudinal relationship in respect to the vertical member 228, but may rotate about the end thereof.

Similar to the previously described modiication, as the wire W is unwound from the reel 250, it is passed through a wire guiding device generally indicated at 251, and is then passed through the hollow shaft 191. After the wire leaves the lower end of the shaft 191, it is passed through an opening 254 formed near one end of the vertical member 228 and out the opposite end thereof, and subsequently out through the die opening 255 of the tensioning mechanism 238.

The operation of this form of the invention is similar to the previously described modification except as is shown in Figure 7, when the vehicle 189 is moved to such a position that the shaft 191 is disposed generally over the end 260 of the beam 261, the shaft 191 is then rotated approximately so that the wire W may thereby be wound about the end of the beam. The ex tent and position of rotation must be determined in relation to the position of the vehicle as it is driven back and forth, in order that tension may be maintained on the wire throughout the winding operation.

It will be appreciated that the radius of the arc described in the vertical member 228 of the cantilever extension 192 may be varied by utilizing a shorter or longer yhorizontal member 227. Such a variation will be necessary when winding beams of substantially different widths. For example, when winding a beam of relatively narrow width, it will be preferable to use a shorter horizontal member 227 in order that the arc described by the vertical member 228 willhave a radius approximately equal to one-half of the width of the beam.

In a third modification disclosed in Figures 8, 9 and 10, it will be yseen that the wire guiding mechanism generally indicated at 275 is of still another form, and the wire guiding die post is raised and lowered by automatically operated jack mechanisms indicated at 277 disposed at each end 278 of the beam B, instead of by a system operated on the vehicle. In addition, wire deflecting devices 279 are utilized to guide the wire W into the longitudinally extending portions 280 of the circumferential groove of the beam previously described, such as that formed about the vertically disposed sides 281 and 282 and the ends 278 of a beam B.

Referring now to Figure 8, a vertically disposed hollow shaft 287 extends through openings 288, 289 and 290 in the horizontal frame members 293, 294 and 295 of the vehicle frame 298. An annular gear 300 is keyed to the center portion of the shaft 287 and has a downwardly extending collar or hub 301. The collar 301 is received within a cylindrical member 303 having a base ange 304 formed -about the opposite end thereof, which is secured to the upper side of the middle horizontal member 294. Ball bearings 307 are supported between corresponding raceways 308, and 309 for-med about the collar or hub 301 of the gear 300 and the inner surface of the cylindrical member 303, respectively. The gear 300 is driven by a worm gear 310 carried by a shaft which in turn is connected by suitable means to the vehicle engine as described in connection with Figs. and 6.

The lower end of the shaft 287 is received within a sleeve 312 having a ange or collar 313 formed about its upper end. The flange 313 is secured by bolts 314 to the underside of the middle horizontal member 294. The lower end of the shaft 287 which extends beyond the opposite end of the sleeve 312 has keyed thereto a circular gear 316. Formed integrally with and extending horizontally from the sleeve are four symmetrical pairs of arms 318, 319, 320 and 321 (see Figure 9), each pair of which rotatably support the four shafts 322, 323, 324 and 325. The pairs of arms 318, 319, 320 and 321 are so arranged that the shafts carried thereby are disposed vertically and at right angles to the arms.

Four symmetrical pairs of gears 330, 331, 332 and 333 are mounted at each end of the vertical shafts 322, 323, 324 and 325, respectively, the upper and lower sets of which are connected by chain belts 335 and 336, respectively. One of the shafts 324 has a third gear 338 keyed 355 is pivotally mounted by suitable means on the lower chain gear 322e, which is drivingly engaged with the shaft gear 316 by a chain belt 339.

A hollow vertically disposed guide post member 345 with a shoulder 345a extending longitudinally along the side thereof is secured to the upper and lower chain belts 335 and 336 by U-shaped clamps 346 and 347 which receive upper and lower portions of the shoulder 345a. The clamps 346 and 347 are secured to the shoulder and chain belts 335 and 336.

Thus, when the shaft 287 and shaft gear 316 are rotated by gear 300, vthe upper and lower chain belts 335 and 336 are rotated at the same rate of speed, and thereby the guide post member 345 is moved in a square shape pattern relative to the longitudinal axis of the shaft 287, as indicated in Figure 9.

With reference to Figures 8 and 10, it will be seen that a post 350 is slidably received within the guide post member 345. In Figure l0 the guide post member 345 and post 350 are shown apart from the chain belts 335 and 336 for simple understanding of the construction.

The guide post 345 is urged downwardly (towards the ground) by a coil spring 352 situated within the upper portion of guide post member 345 and which abuts a plunger 351 formed about the upper end of the post 350.

As in the previously described modilications, a die box 355 is pivotally mounted by suitable means on the lower end of the guide post 350. In most respects the die box 355 is the same as the previously described except it will be noted that a set of rollers 356 are rotatably mounted across the undersurface 357 of the die box 355 and a rod 358 extends horizontally away from the outwardly facing side 359 thereof. The purpose of these parts will be subsequently described.

The Wire W carried by reel 358 is directed by the wire guiding mechanism 359 down through the center of shaft 287 and then upwardly by guiding mechanisms 359a and 359b secured to the side of the wire guide post member 345. Next the wire W is directed downward through the member 345 and guide post 350 and finally out through the die box 355.

The wire deliecting devices generally indicated at 279 are mounted adjacent to the vertically disposed sides 281 and 282 of the beam B. As will be seen in Figure 10, the devices 279 include a pair of downwardly facing arcuate members 360 and 361 which are bolted at 362 to a laterally extending member 363. The arcuate members 360 and 361 which have brackets 364 secured to each side thereof, are secured to the sides 281 and 282 of the beam B by means of spikes 365 which are driven through openings in the brackets 364 into the beam. Also, the lateral member 363 may be similarly secured to the upper surface 366 of the beam B. The deflectors may also be secured to the beam by clamping.

Each of the arcuate members 360 and 361 has inwardly extending shoulders 369 formed integrally with an inwardly facing side 370 of adjacent members which are received within the narrow portion of the circumferential groove 280. The shoulders 369 are of slightly smaller width than the groove 280 and extend nearly to the footing thereof.

It will be understood, of course, that the wire guiding devices 279 may be of modied design, as for example, as shown in Figure 8, the laterally extending member 363 (of Figure l0) may be omitted, and each of the arcuate members 360a having brackets 364a formed integrally with upwardly facing side thereof, are secured to the sides 281 and 282 of the beam B by spikes 365. Also, it is to be understood that such wire guiding devices 279 may be utilized in previously described modilications of this invention if so desired. A more detailed description of those devices may be found in my copending application Serial No. 335,233, tiled February 5, 1953.

With particular reference to Figure 10, it will be seen that the jack mechanism generally indicated at 277 in.

cludes a jack 374 which supports a horizontal member 375 extending laterally across the ends 278 of the beam B. Inclined members 378 and 379 are hinged at 380 and 381 to each end 384 and 385 of the member 375, and extend downwardly towards the ground. The jack 374 is raised and lowered by a gear and pawl arrangement generally indicated at 390 which is mounted on the end of the jack drive shaft 391. The pawl 392 is pivotally mounted on a lever 394. The lever 394 in turn is pivotally mounted at its lower end 396 to the end of the jack shaft 391, and extends upwardly to above the level of the rod 358 mounted on the die box 355. Thus each time the rod 358 strikes the lever 394, the latter is moved and thereby the jack is raised or lowered.

In the operation of the modilication shown in Figures 8, 9 and 10, it will be assumed that the wire guide post 350 is presently being moved by the vehicle towards the right in Figure 8 toward the end 278 of the beam B, and is now in position shown in dotted lines at 35011 to the left of the beam in Figure 10.

When the post 350 is in this position, it will be noted that the wire W (see Figures 9 and 10) extending from the die box 355, extends at an angle from the vertical side 281 of the beam B. As the post 350 is moved towards the end 278 of the beam B, the rollers 356 on the die box 355 strike the inclined member 378 and the latter is thereby raised to the level (against the tension of spring 352) of the horizontal member 375.

When the wire guide post 350 reaches a position slightly beyond the end 278 of the beam B, it is moved laterally in respect thereto by drivingly engaging the shaft gear 300 with the vehicle engine and thereby rotating the shaft 287 and the chains 335 and 336. As the wire guide post 350 is moved laterally in respect to the beam B, the wire W' strikes the arcuate member 360 of the wire deecting device 279 and is thereby deposited into the groove 280. The die box 355 pivots counterclockwise by means of the tension on the wire W striking the corner 397 of the beam, and as the die box 355 is moved across the horizontal member 375, the wire W is deposited at the desired level about the ends 278 thereof.

When the wire guide post 350 has been moved laterally to the opposite side 282 of the beam B and a slight distance in the opposite direction as indicated in dotted lines at 3501: in Figures 9 and 10, the vehicle may then be moved in the opposite direction, i. e., to the left as viewed in Figure 8. As the wire W strikes the opposite corner 398 of the beam B the die box 355 again pivots counterclockwise. While the die box 355 is moved along the opposite inclined member 379, the coil spring 352 urges the guide post 350 downwardly to its initial position.

It will also be noted that as the die box 355 is moved across the horizontal member 375, the rod 358 strikes the jack lever 394, and thus the jack is lowered a sucient amount so that the next succeeding loop of wire will be deposited just beneath the preceding loop on the end of the beam.

In connection with this modification it is to be understood that the wire guiding drive mechanism 275 may be operated by other means besides the vehicle engine; for example by an independent electric motor. Also it will be understood that the movement of the guide post 350 may be automatically controlled as well as being manually operatable by the vehicle driver.

It is to be understood that in any of the modications the vehicle may be towed by a chain or belt rather than being self-propelled, and in this connection tracks may be provided to guide the wheels of the vehicle so that the latter is maintained in the proper position in respect to the structure about which the wire is wound.

Furthermore, it is to be understood that the various structural parts of this device are susceptible to considerable modication Without departing from the basic concept of this invention. Therefore, the form of the invention described above should be considered as illustrative and not as limiting the scope of the following claims.

I claim:

l. Apparatus for prestressing a structure with wire comprising a wire conveying vehicle movable in a xed path relative to and over said structure, swivel means carried by said vehicle for guiding the Wire to position it in the desired pattern on said structure as said vehicle is moved lrelative thereto, means for moving the swivel means relative to the vehicle to adjust the height thereof, means for displacing the swivel means laterally relative to the vehicle, and means to tension the wire.

2. Apparatus for prestressing a structure with wire comprising a vehicle movable relative to and over said structure, means for supporting a quantity of wire on said vehicle, a movable wire'guiding means mounted on said vehicle, means to vary the position of said wire guiding means relative to the vehicle in both vertical and horizontal directions to position the wire in the desired pattern on said structure as said vehicle is moved relative thereto, the vertical position of said wire guiding means determining the height at which -the wire is positioned on the structure, and the horizontal movement of the wire guiding means relative to the vehicle serving to pay out the wire independently of and at right angles to the direction of movement of the vehicle, and means to tension the wire as it is positioned on the structure.

3. Apparatus as described in claim 2 for prestressing a structure having longitudinal grooves extending between 10 each end thereof, said apparatus including wire deecting means to guide said tensioned wire into the grooves as said wire guiding means is moved relative thereto.

4. Apparatus for prestressing a structure having longitudinal grooves extending between each end thereof to receive tensioned wire, comprising a vehicle, means to move said vehicle relative to and over said structure, means for supporting a quantity of wire on said vehicle, a Wire guiding means mounted on said vehicle to position said Wire on said structure, actuatable means for moving the wire guiding means relative to the vehicle to adjust the height at which the wire is dispensed and positioned on said structure, and actuatable means to move said wire guiding means laterally in respect to the longitudinal axis of said vehicle, and means to tension the wire as it is positioned on said structure.

5. Apparatus for prestressing structural members with wire comprising a traction driven, self-propelled vehicle, means to steer said vehicle, means for carrying wire on said vehicle, means for tensioning said wire, a movable arm carried by and extending beneath said vehicle, a wire guiding means pivotally mounted on said arm, means for moving said arm and wire guiding means laterally in respect to said vehicle, means for raising and lowering said wire guiding means, to thereby deposit tensioned wire in the desired pattern on said structural member as said vehicle is moved relative to and over said structure.

6. Apparatus for prestressing an elongated stationary structure having sides extending between each end on which to position tensioned wire, comprising `a traction driven, self-propelled vehicle, means for carrying wire on said vehicle, means for tensioning said Wire, an arm extending generally vertically beneath said vehicle, wire guiding means pivotally mounted on said arm, and horizontally disposed guide means for bodily translating said `arm laterally in respect to said vehicle, to thereby guide said tensioned wire across the ends of said structure as the vehicle is moved relation to and over the structure.

7. Apparatus for prestressing with wire an elongated beam xedly positioned relative to the ground, said beam having grooves on the sides near the bottom, comprising a four-wheeled traction driven vehicle having a high center to clear the beam as the vehicle is driven back and forth on the ground over the beam from one end of it to the other, means mounting a supply of Wire on the vehicle, means for tensioning the wire, means on said vehicle to displace the wire laterally as the vehicle is driven back and forth over the beam to position the wire alternately on the sides of the beam, and means to displace the wire vertically to position it in said grooves.

8. Apparatus for prestressing a structure with wire comprising a wire conveying vehicle movable in a fixed path relative to and over said structure, swivel means carried by said vehicle for guiding the wire to position it in a desired pattern on said structure as said vehicle is moved relative thereto, means for moving the swivel means relative to the vehicle to adjust the height thereof, means for displacing the swivel means laterally relative to the vehicle, and means to tension the wire.

9. Apparatus for prestressing a structure with wire comprising a vehicle movable relative to and over said structure, a movable wire guiding means mounted on said vehicle, means to vary the position of said wire guiding means relative to the vehicle in both vertical and horizontal direction to position the wire in a desired pattern on said structure as said vehicle is moved relative thereto, the vertical position of said wire guiding means determining the height at which the wire is positioned on the structure, and the horizontal movement of the wire guiding means relative to the vehicle serving to pay out the wire independently of and at right angles to the direction of movement of the vehicle, and means to tension the wire as it is positioned on the structure.

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS Lingenfelter Sept. 4, 1906 Crane .Tune 24, 1919 Wood Apr. 26, 1921 Lockwood July 22, 1941 Kennisori Feb. 11, 1947 Bolton Aug. 30, 1949 FOREIGN PATENTS France May 30, 1949 

